1. Field of the Invention
This invention relates to a system for recirculating a portion of the fumes evolved from a chemical process and, more particularly, to a metal pickling process evolving fumes, such as hydrogen chloride, in order to improve the cleanliness of fumes exhausted to the atmosphere.
2. Description of the Prior Art
Prior to the present invention, fumes produced in a pickling tank were captured and processed through a scrubbing tower, with water, to remove acid fumes from the transporting air. Such scrubbers have a fixed efficiency (1-fume concentration out/fume concentration in) based on the incoming acid concentration, gas flow through the scrubber, and scrubber water concentration, as well as other scrubber design details. A typical scrubber efficiency is between 90% and 99.5%.
A significant limitation of such systems is that the incoming gas is cleaned to near the same concentration of acid as that in the water in the scrubber so that the scrubber no longer can absorb more fumes, and its efficiency is thus effectively capped. Also, higher scrubber efficiencies require more fresh water which, being contaminated with acid, must be treated for acid removal before disposal.